At present, with the increasing development and popularization of electric control systems (e.g. an electric control system in a pure electric/hybrid vehicle), charging a power battery pack of a vehicle (e.g. a pure electric/hybrid vehicle) using DC current via a charging station or a charging pile is becoming more and more important.
In a prior technical solution, typically two high voltage relays (e.g. high voltage relay S1 and S2 in FIG. 1) are added into a high voltage bus loop which is used for DC charging, thus, in the case of non-DC charging, the two high voltage relays is disconnected by a controller, to ensure that the high voltage electricity will not be exposed to the outside and result in accidents.
However, the above prior technical solution has the following problems: due to the physical/mechanical features of the relay, the contacts of the two high voltage relays are likely to adhere (i.e., loose efficacy since keep staying in a closed state for a long time) in the course of operation, in this case, the high voltage electricity on an internal high voltage circuit may be exposed to the outside, thereby potential accidents may be caused.
Hence, there is a need for the following: providing a diagnosis system for vehicular DC charging relay with high diagnostic efficiency and low cost.